Conventional aircraft engines utilize reciprocating engines, turbine driven propeller engines, or turbine engines which deliver thrust as a result of a combination of fan action and jet thrust. Reciprocating engines require very high maintenance and turbine engines are very expensive to manufacture because of the exotic materials used in the hot section of the engine. Reciprocating and turbine engines rely entirely on the combustion of a chemical fuel for their operation.
Recently, because of advances in electric motor technology and battery energy density, short range small aircraft have been developed that are quiet, non polluting, and have ultra low maintenance requirements. These aircraft, however, have very short flight range because the energy density of lithium ion batteries is only about 190 watt hours per kilogram. Hydrocarbon fuels have energy densities in the range of 12,000 watt hours per kilogram. So it is obvious that even with advances in battery energy density, electrically operated aircraft will have limited distance capabilities.
It is, therefore, desirable to retain the beneficial operating characteristics of the electric propulsion system while increasing range.